Currently, microelectronic components such as by way of examples only, semiconductor device, integrated circuits and flat panel displays are fabricated in a rectangular building-like facility which can typically be a 3-level structural building with outside dimensions of, for example, about 600 feet by 180 feet. The first or subfab floor generally contains the electric and mechanical equipment such as pumps and chemical/gas handling piping, the second or fab floor generally holds the clean room under ultra clean condition and the various processing stations which can accomplish processes such as lithography, etching, sputtering, chemical vapor deposition, diffusion, and the like, while the third floor handles air circulation/condition. Generally the facility is laid out with a longitudinal clean room which can run the length of the structure, up to 600 feet. Various work stations are located substantially perpendicularly to and along each side of the clean room. An automated material handling system is used to carry the wafers and substrates which are being processed up and down the clean room, and perpendicularly to the longitudinal direction of the clean room, to the equipment of the various processing steps. U.S. Pat. No. 5,611,861 issued to Shimoyashiro et al is directed to the conventional arrangement.
Such an arrangement is expensive to build and operate from a number of standpoints. First, the external shell of the building has to be designed so that the outer walls support the entire roof so that there are no interior posts to interfere with the positioning of the equipment in the fabrication process. Such an arrangement requires that the roof be supported by an expensive and complicated support system. Second, such a facility resides with the actual operation of the facility itself. In such an arrangement, the automated system for moving the wafers from station to station must travel up and down in the elongated clean room area to the stations such as stockers in order to reach the next available equipment for the required process. This will require the automation system to transport the wafers great distances.
Further, it is not convenient to expand such a typical fabrication facility. Generally, it would be simpler just to duplicate the complete fabrication facility in an adjacent area. Any modification to such facilities would require substantial changes, including the movement of walls, process equipment, gas and chemical circulation systems and the like. Further to retrofit, replace or upgrade existing equipment in such a facility would require that the facility be shut down and that equipment and structure be moved in order to access equipment that is to be retrofitted or replaced.
A futuristic design for a fully automated fabrication facility was proposed in a paper from Tohoku University, entitled Circular Centered Single-Column Fab. In this design, a circular dome-shaped building was proposed which is supported by an outer peripheral wall and a central tower. In this facility, the fabrication equipment is located outwardly of the central tower. Such equipment includes photolithography stations and the like. Such a configuration was never constructed and if it had been, it would have been extremely expensive due to the large dome-shaped roof required and the structure necessary to hold that roof in place. Further, safety would be an issue as special safety quarters would have to be constructed in order to allow for exit through the periphery of the structure. A further disadvantage is that the support services for such a plant such as gas plants, ultra pure water plants, chemical plants, and air-conditioning plants are located outside the circular area of the dome housing and thus increase the distance needed for distribution piping and conduit to serve the fabrication facility. Further, an expansion of such a facility would be difficult in that the outer walls, being required to support the roof, cannot be easily removed or modified.
An alternative design set forth in U.S. Pat. No. 5,344,365 issued to Scott et. al relates to a modification over a conventional semiconductor manufacturing facility by means of replacing a rectangular building with a circular, multi-story one and accommodating the work piece transportation system in its central silo. Since the flexibility in expanding and modifying the facilities is still limited under such configuration and the building's existence is indispensable, time and cost spent for constructing and maintaining this facility are not reduced. Furthermore, because the manufacturing area, work piece transportation system and facility supply system are all accommodated in a building, vibration produced, for example, from the transportation system when the work piece is conveyed will be readily transmitted to the manufacturing area and facility supply system.
Hence, it is desired to provide one or more semiconductor device fabrication systems that depart from the above limitations, reduce production cost, and enhance accessibility in facility construction and maintenance. This invention discloses a creative semiconductor device fabrication system for use in the field of microelectronic component fabrication process as follows.